pager

func Main ¶

func Main(ctx context.Context, fn func(ctx context.Context, out io.WriteCloser) int) int

Main implements paging using commands "less" or "more" if they are available. If os.Stdout is not terminal or less/more are not available in $PATH, Main calls fn with out set to os.Stdout and returns its exit code. Otherwise creates a pager subprocess, directs its stdout to os.Stdout and calls fn with out set to pager stdin. fn's context is canceled if the user quits pager.

If fn returns non-zero exit code before pager exits, Main returns that exit code. Otherwise Main returns pager's exit code. It is a race between the user hitting q and fn failing.

Example:

func main() int {
	return Main(context.Background(), func(ctx context.Context, out io.WriteCloser) int {
		for i := 0; i < 100000 && ctx.Err() == nil; i++ {
			fmt.Fprintln(out, i)
		}
		return 0
	})
}